Recently, in hybrid vehicles, electric vehicles, and so on, rotating electric machines have been increasingly used as driving apparatuses for vehicles in view of the environmental problem. It is required that the rotating electric machine mounted in a vehicle be a space-saving one, i.e., be small in size because the mounting space is limited. Further, it is required that the rotating electric machine have high power in order to improve the driving performance of the vehicle. In order to reduce the size of the rotating electric machine as well as to increase the power thereof, it is conceivable to increase the electric current flowing through the coil in the stator. To that end, it is necessary to secure the cross section of a coil used in the stator, and therefore it has been proposed to use a coil having a rectangular conductor.
This rectangular conductor includes an insulating film on its periphery. The rectangular conductor is disposed in slots, which are formed at regular intervals in the circumferential direction of the stator core, in a predetermined order so that a three-phase coil having U-, V-, and W-phases is formed. In order to electrically connect rectangular conductors forming these phases, it is necessary to remove the insulting film at the ends of the rectangular conductors and join the ends of the rectangular conductors to each other.
When the insulating film at the end of the rectangular conductor is removed, if the insulating film is cut from the four surfaces on the short sides and the long sides in the cross section of the joint lead wire, the peripheral surface itself of the rectangular conductor, which has been originally covered with the insulating film, is also cut and hence the rectangular conductor becomes thinner. Therefore, the size of the welding cross section is reduced. Consequently, there has been a problem that the end of the rectangular conductor is deformed after the welding of the end of the rectangular conductor and hence the welding quality deteriorates.
To solve this problem, Patent Literature 1 discloses a method in which after only the insulating film is cut from the short sides and the long sides of the joint lead wire, the insulating film remaining at the four corners of the rectangular conductor is cut (first method). Specifically, after the insulating film on the long sides at the end of the joint lead wire is cut, the insulating film on the short sides of the joint lead wire is cut. After that, the exposed four corners of the rectangular conductor are chamfered. In this way, it is possible to prevent the thickness of the rectangular conductor from being reduced.
However, in the above-described first method, since the four corners of the rectangular conductor are chamfered, burrs are formed at the four corners of the rectangular conductor. Therefore, there has still been a problem that the welding quality cannot be ensured.
Therefore, as a method for solving this problem, Patent Literature 1 discloses a method in which after the insulating film is cut from the peripheral surface of the rectangular conductor, the insulating film is cut from the side surfaces of the rectangular conductor toward the junction surface (second method). Note that the junction surface means, in a cross-section of a rectangular conductor, a surface that is joined with another rectangular conductor. Further, the side surfaces mean two surfaces adjoining the junction surface. In this way, when the junction surfaces of a pair of rectangular conductors are joined to each other, burrs protruding from the junction surfaces are sandwiched between the junction surfaces of the pair of rectangular conductors so that they do not protrude from the periphery of the pair of rectangular conductors. As a result, it is possible to improve the welding quality (joint quality) of the rectangular conductor.